Add libpolicy stub-implementation to Android.mk

libpolicy is installed directly as "policy" in Chrome OS, so this patch
moves the chromeos/policy directory one level up to match what users will
see in installed Chrome OS include dir. A new libchromeos-policy shared
library is included in the Android.mk.

BUG: 23555535
TEST=emerge-link libchromeos; `mm` in aosp.

Change-Id: I0d62a1651632242a08309ca2c00056837a5280a6
diff --git a/libpolicy.gypi b/libpolicy.gypi
index b22d690..25b251d 100644
--- a/libpolicy.gypi
+++ b/libpolicy.gypi
@@ -7,11 +7,11 @@
         {
           'destination': '<(SHARED_INTERMEDIATE_DIR)/include/policy',
           'files': [
-            'chromeos/policy/device_policy.h',
-            'chromeos/policy/device_policy_impl.h',
-            'chromeos/policy/libpolicy.h',
-            'chromeos/policy/mock_libpolicy.h',
-            'chromeos/policy/mock_device_policy.h',
+            'policy/device_policy.h',
+            'policy/device_policy_impl.h',
+            'policy/libpolicy.h',
+            'policy/mock_libpolicy.h',
+            'policy/mock_device_policy.h',
           ],
         },
       ],